It is known that quartz crystal blanks can be chemically polished by etching in a fluoride type etchant over a broad range of conditions. The quality of chemical polish depends primarily on the surface finish prior to etching, the depth of etch and the quality of quartz used. The speed of polishing depends primarily on the temperature of the etching bath for a given etchant.
The above set forth conventional method of chemically polishing quartz crystal blanks though generally satisfactory does have certain deficiencies. In particular, in the case of an SC-cut doubly rotated quartz crystal blank which has widespread use in resonators and oscillators, the quartz blank has a fast etch side and a slow etch side. When the conventional method of polishing is used, the slow etch side of the crystal lags the fast etch side so that it does not polish to the same degree of surface smoothness even though etched to the same depth of etch.
In the case of an AT-cut quartz crystal blank which also has widespread use in resonators and oscillators, another deficiency arises. That is, while it is well known that sodium hydroxide will etch quartz crystals, it has not been demonstrated that it can be used to chemically polish lapped AT-cut blanks. This may be due to the fact that the reaction rate is so slow that it is not practical to do so with the conventional method.
Another problem with the conventional process is the evaporation of etchant which causes the etch rate of the etchant to constantly change.
Another difficulty with the conventional etching method has been its inability to practically use dilute solutions of etchants.